A group of peptides with melanotropic and lipolytic properties has long been known to be present in the pituitary gland. This laboratory discovered in 1970 another group of melanotropic-lipolytic peptides in extrahypophyseal regions of mammalian brain, and in 1979 a new melanotropic peptide in the pituitary itself. The objectives of this project are to determine the chemical structures and physiologic functions of all naturally occurring hypophyseal and extrahypophyseal melanotropic-lipolytic peptides.